TGF-?? MIMICS AND ANTI-TGF-?? REVERSES THE FIBROGENIC AND NEPHROTOXIC EFFECTS OF CYCLOSPORINE

306 The main limitation to cyclosporin's (CsA) use is the associated nephrotoxicity. We have previously demonstrated that CsA induces transforming growth factor-beta (TGF-β), a multifunctional cytokine which has anti-proliferative as well as fibrogenic properties, both in-vivo and in-vitro. This study was designed to test the hypothesis that TGF-β mediates the upregulation of fibrogenic proteins which could lead to the nephrotoxic effects of CsA. Mice (n = 6) treated with CsA (25 mg/Kg) i.p. daily for 7 days were sacrificed either at 10 or 28 days post last injection. In an identical CsA protocol, a second group of mice was also treated with anti-TGF-β monoclonal antibody on day 7. Control mice for these two groups were treated with oil. To compare the effects of CsA with TGF-β, a third group of mice were also treated with purified TGF-β (150 ng/day for 3 days) and control mice for this latter group were injected with PBS-BSA. The nephrotoxic effects were studied both by direct histopathological changes in periodic acid schiff's reagent stained thin kidney sections as well as intra-renal expression of TGF-β, collagen and fibronectin genes by RT-PCR. TGF-β protein expression in these kidneys was also investigated using immunohistochemistry. CsA induced intra-renal expression of TGF-β, collagen, and fibronectin genes, the induction was neutralized in mice treated with anti-TGF-β antibody. TGF-β protein expression was observed in the tubules, outer cortex and interstitium of the kidneys treated with CsA but not in mice treated with CsA and anti-TGF-β antibody and controls. CsA and TGF-β treatment caused similar histopathological changes of vauolization of epithelial cells in the proximal convoluated tubules and thrombotic microangiopathy (arrows). Manipulation of TGF-β levels by anti-TGF -β mAb treatment could alter in-vivo effect of CsA and changes of vauolization of epithelial cells in the proximal conovulated tubules and thrombotic microangiopathy were not see (arrow). These data demonstrate that the CsA induced fibrogenic gene expression and early histologic changes in the kidney appear to be mediated by TGF-β, suggesting a role for this cytokine in CsA induced nephrotoxicity.Figure